Current research on the uterine action of prostaglandins indicates that an intimate relationship exists between this uterotonic agent and the hormone, oxytocin and that these two endogenous substances may play an important role in the process of parturition. Indirect evidence suggests that the uterine stimulating action of oxytocin and, possibly also other uterotonic therapeutic agents may act by stimulating prostaglandins production and/or release in the uterus. The objectives of this proposed project are: (1) To present direct experimental evidence for an oxytocin-induced release of prostaglandins in the uterus. (2) To define the pharmacological characteristics and to determine the specificity of oxytocin-induced release of prostaglandins. (3) To ascertain whether the release of prostaglandins may be a common path in the chain of myometrial activation evoked by various uterotonic agents. Experiments will be performed on isolated uteri from non-pregnant rats and rats at various stages of gestation. The effects of oxytocin, oxytocin inhibitors and other uterotonic agents on uterine prostaglandin production and release will be determined by measuring myometrial tissue content and the rate of release of prostaglandins. Bioassays and thin-layer chromatography will be employed for the quantitation and identification of prostaglandins.